1. Field of the Invention
This invention relates to typewriters utilizing variable color display.
2. Description of the Prior Art
A display device that can change color and selectively display charcters described in my U.S. Pat. No. 4,086,514, issued on Apr. 25, 1978 and entitled Variable Color Display Device, includes display areas with three light emitting diodes for emitting variable portions of light signals of respectively different primary colors, which are blended within each display area to form a composite light signal.
Monochromatic display typewriters have flourished in recent years and are extensively used. Such display typewriters, however, are capable of visually presenting only the typed text. They are not capable of simultaneously indicating the typing speed and accuracy.
An electronic typewriter disclosed in U.S. Pat. No. 4,323,315, issued on Apr. 6, 1982 to Filippo Demonte et al. and entitled Electronic Typewriter with Display Device, includes a monochromatic display which is capable of displaying characters with different kinds of emphasis.
A microprocessor-based display controller for 5.times.7 matrix monochromatic display is described in Hewlett-Packard application note 1001, pages 398-413 issued in 1980 and entitled Interfacing the HDSP-2000 to Microprocessor Systems.
A device for indicating typing speed and rhythm disclosed in U.S. Pat. No. 2,717,688, issued on Sept. 13, 1955 to James A. Brooks and entitled Typing Speed and Rhythm Indicating Apparatus for Typewriters, includes a light bulb which remains continuously lit when the typist keeps depressing keys with sufficient speed and uniformity.
An electronic typewriter described in West German Pat. No. 3,534,569, issued on Apr. 3, 1986 to O. Flugel et al. and entitled Electronic Typewriter with Print Speed Monitoring, includes a monochromatic display for digitally indicating typing speed.
A word processing system disclosed in U.S. Pat. No. 4,136,395, issued on Jan. 23, 1979 to Robert A. Kolpek et al. and entitled System for Automatically Proofreading a Document, includes a dictionary memory and comparator for detecting spelling errors.
A variable color display typewriter is unknown to the inventor.